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have streamflow gauges situated within 20 km of the coast, resulting in difficulties in
evaluating river flow into estuaries. Furthermore, 59 of the 73 rivers draining into
estuaries have no streamflow gauges at all. The Division of Earth, Marine and
Atmospheric Science and Technology, CSIR, PO Box 320, Stellenbosch, 7599,
accordingly provided simulated monthly virgin runoff data (at the mouth) for 69 rivers in
NatallKwaZulu draining into estuaries. The data-span covered the years 1921 - 1975.
The runoff data were derived from reports produced by the then Hydrological Research
Unit, University of the Witwatersrand*. For further details see Perry (1986)**.
10.14 International rivers of Natal and environs***
Recommendations drawn up by the International Law Association in Helsinki in 1966
(known as the Helsinki Rules), concern the joint use of water common to two or more
states****. The Helsinki Rules define an international drainage basin (also termed
an international watercourse system) as a geographical area extending over two or more
states; and which is determined by the watershed limits of the system of waters ­
including surface and groundwaters - flowing into a common terminus. A basin state (also
known as a system state), is defined as a state whose territory includes a portion of an
international drainage basin. Each basin state is entitled (within its territory), to a
reasonable and equitable share of the water of an international drainage basin which can
be beneficially used. The principle of equitable sharing implies that the maximum benefit
with the minimum disadvantage should accrue to each basin state, following from the use
of the common water. This does not mean that every state must necessarily receive an
*
**
***
****
See Middleton, B.J., lorentz, S.A., Pitman, W.V. and Midgley, D.C., 1981. Surface water resources
of South Africa, VOl V: drainage regions MNPORST. The eastem Cape Part 1 (Text), various pages,
and Part 2 (Appendices), various pages, HRU Report No. 12/81, Hydrological Research Unit,
University of the Witwatersrand, Johannesburg, as well as Pitman, W.V., Middleton, B.J. and
Midgley, D.C., 1981. Surface water resources of South Africa, VOl VI: drainage regions UVWX.
The eastem escarpment Part 1 (Text), various pages, and Part 2 (Appendices), various pages, HRU
Report No. 9/81, Hydrological Research Unit, University of the Witwatersrand, Johannesburg.
See Perry, J.E., 1986. Basic physical geographyihydro data for Natal "estuaries", NRIO Data Report
No. 0 8607, Sediment Dynamics Division, Coastal Engineering and Hydraulics, National Research
Institute for Oceanology, CSIR, Stellenbosch, 6 p. + app.
Discussion based on Anonymous, 1986. Management of the Water Resources of the Republic of
South Africa, Department of Water Affairs, Pretoria, various pages.
An interesting sub-discipline is that of "hydropolitics" namely, the study of political interactions
between countries, especially in water-scarce regions. There are those who believe that future warsin
certain parts of the world - will be fought over water.